The invention pertains to machine tool tracer control systems, and in particular, wherein a two-dimensional template may be utilized in the machining of a three-dimensional workpiece contour.
Tracer controlled machine tools, such as milling machines, commonly utilize a tracer, usually air or hydraulically controlled, to sense a three-dimensional template or pattern for controlling the relative position of the cutting tool and workpiece to duplicate the template contour upon the workpiece. Significant cost savings is experienced by the use of tracer controlled machine tools in that a plurality of irregular contoured surfaces may be accurately machined upon a plurality of workpieces with a minimum of attention and supervision by the machine operator.
While tracer controlled machine tools have the advantage of accurately duplicating a template surface on a plurality of workpieces, the three-dimensional template or pattern traversed by the tracer must be very accurately produced, even though formed of wood, plastic or other material which is relatively easy to machine and shape. Due to the relatively high cost of producing an accurate three-dimensional pattern or template the economies of tracer control machines are only experienced with relatively high production machining operations wherein one template may be used to produce many workpiece surfaces. As a practical matter, tracer control machine tools are not economically usable with short run machining operations wherein only a relatively limited number of contoured surfaces are to be machined, due to the cost of producing the necessary three-dimensional template. Accordingly, tracer control machine tools, in the past, have not been economically used in low production machining operations, and the advantages of this type of machine tool have been limited to multiple machining operations wherein the cost of producing a relatively complicated three-dimensional template is justified.
Attempts have been made to form three-dimensional contours from two-dimensional templates, such as shown in U.S. Pat. Nos. 2,933,985; 3,230,810 and 3,640,182, but such patented devices require two templates and tracers and are expensive and not readily adaptable for "short run" production.